Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


NIWA survey work helps assess Kaikoura tsunami risks

22 March 2013

NIWA survey work helps assess Kaikoura tsunami risks

Surveying work carried out by NIWA scientists this week is helping provide new insights into the tsunami risk from undersea landslides in the Kaikoura Canyon.

The Kaikoura Canyon is a submarine canyon just off the east coast of the South Island, and connects the continental shelf with deep ocean basins to the north. Submarine landslides are one of the main processes that create submarine canyons. Landslides in the head of Kaikoura Canyon are thought to occur about once every 200 years on average.

Modelling by NIWA scientists in 2006 looked at the potential severity of tsunamis off the Kaikoura coast, either triggered by submarine earthquakes or as a result of a submarine landslide of sediment occurring at the head of the Kaikoura canyon.

The modelling showed that a submarine landslide at the head of the canyon would cause a significant tsunami that would arrive in South Bay with very little warning, with the crest of the wave about 13 metres above sea level (see below for more details).

Now NIWA scientists are using new technology to determine the size, shape and physical character of the sediment deposit in order to further assess the tsunami hazard if a landslide occurred.

“This is the most dynamic and active submarine canyon on the New Zealand margin, coming to within 500 metres of the shoreline and dropping to 1000 metres deep within 5 kilometres of the shoreline,” says NIWA Marine Geologist Dr Joshu Mountjoy.

“Kaikoura is a very active seismic region and with the potential for large earthquakes, any unstable sediment could collapse during a good shake and generate a tsunami. We need to know just what the hazard is from such events to ensure the resilience of coastal communities.”

By collecting multibeam bathymetric data, boomer seismic reflection data and sediment core samples, the team mapped the shape of the seafloor, determined the thickness of the sediment and collected sediment samples to analyse how much sediment is accumulating in the canyon head due to ocean currents and large storm activity.

“Since the previous work was carried out on the Kaikoura Canyon head in the 1990s, new scientific techniques now allow us to determine the rate at which sediment has accumulated here over the last century” says NIWA scientist Dr Alan Orpin “and this has big implications for how much sediment accumulates in the canyon head” he adds.

Geophysical data collected this week will be combined with a geotechnical field and laboratory investigation of the sediment deposit and then fed into new tsunami source and inundation modelling to get a better idea of the scale of the potential tsunami risk.

“The best result from this work would be that the amount of sediment at the head of the canyon has been over-estimated in the past and the hazard is much lower that thought – but we won’t know the answer to that until we have analysed the new data collected this week,” says Dr Mountjoy.

NIWA’s survey vessel Ikatere was used to do the survey work, which is co-funded by NIWA and Environment Canterbury.

More information:

What did the 2006 modelling show if there was a submarine landslide from head of Kaikoura canyon?

The moment the landslide happens would be dramatic for anyone in a boat off the coast. Water around the canyon head walls would appear to be sucked down creating a large hole with a pinnacle of water rising in the centre. Large waves radiate out, some following of the direction of the sliding mass of sediment below. However, the biggest waves radiate back towards Goose Bay and Oaro.

All this happens very quickly. The tsunami’s first wave arrives at Goose Bay just one minute after the landslide starts. The wave crest is about 13 metres above sea level. A smaller wave, slightly less than 2 metres high, reaches Kaikoura about 15 minutes after the landslide, and a sequence of waves arrive at the township for almost an hour.

How likely are such tsunamis?

Kaikoura is in a highly seismically active region, but not all earthquakes are of sufficient magnitude to trigger tsunamis.

The recurrence intervals on the submarine faults in this study are long – in the order of tens of thousands of years. In general, the recurrence intervals for other faults in the area are much shorter. Submarine landslides in the canyon, however, are thought to occur about once every 200 years on average.

For more information about NIWA’s research vessel Ikatere – click here.

ENDS

© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Economic Update: RBNZ Says Rate Cut Seems Likely

The Reserve Bank will likely cut interest rates further as a persistently strong kiwi dollar makes it difficult for the bank to meet its inflation target, it said. The local currency fell. More>>

ALSO:

House Price Action Plan: RBNZ Signals National Lending Restrictions

The central bank wants to cap bank lending to property investors with a deposit of less than 40 percent at 5 percent and restore the 10 percent limit for owner-occupiers wanting to take out a mortgage with a deposit of less than 20 percent, according to a consultation paper released today. More>>

ALSO:

Sparks Fly: Gordon Campbell On China Steel Dumping Allegations

No doubt, officials on the China desk at MFAT have prided themselves on fashioning a niche position for New Zealand right in between the US and China – and leveraging off both of them! Well, as the Aussies would say, of MFAT: tell ‘em they’re dreaming. More>>

ALSO:

Loan Sharks: Finance Companies Found Guilty Of Breaching Fair Trading Act

Finance companies Budget Loans and Evolution Finance, run by former 1980s corporate high-flyer Allan Hawkins, have been found guilty of 106 charges of breaching the Fair Trading Act for misleading 21 borrowers while enforcing loan contracts. More>>

ALSO:

Post Panama Papers: Govt To Adopt Shewan's Foreign Trust Recommendations

The government will adopt all of the recommendations from former PwC chairman John Shewan to increase disclosure and introduce a register for foreign trusts with new legislation to be introduced next month. More>>

ALSO:

The Price Of Cheese: Cheddar At Eight-Year Low

Food prices decreased 0.5 percent in the year to June 2016, influenced by lower grocery food prices (down 2.3 percent), Statistics New Zealand said today. Compared with June 2015, cheese prices were down 9.5 percent, fresh milk was down 3.9 percent, and yoghurt was down 9.2 percent. More>>

ALSO:

Financial Advisers: New 'Customer-First' Obligations

Goldsmith plans to do away with the current adviser designations which he says have been "unsatisfactory" in that some advisers are obliged to disclose potential conflicts of interest and act in their customers' best interests, but others are not. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news